Orchestrating the skeleton-filler architecture of soy protein isolate gel via chitosan oligosaccharide chain length

Orchestrating hierarchical protein assembly is pivotal for tailoring plant-based food textures. This study elucidates a skeleton-filler mechanism by modulating chitosan oligosaccharide (COS) chain length during preheated soy protein isolate gelation. Spectroscopic and microscopic analyses revealed that long-chain COS induced substantial unfolding, increasing ordered β-sheets to 59.2% and promoting denser aggregate assembly. Critically, analyses of ultracentrifugation fractions confirmed that long-chain COS facilitated the formation of disulfide-crosslinked large aggregates (LAs). These LAs, serving as rigid skeletons, exhibited larger hydrodynamic radii but reduced surface hydrophobicity due to hydrophilic COS shielding, while small aggregates acted as interstitial fillers. This architectural optimization accelerated mesoscopic dynamics and elevated the storage modulus by 2.3-fold. Furthermore, low-field nuclear magnetic resonance and magnetic resonance imaging demonstrated restricted water mobility within this dense network, evidenced by a shortened relaxation time of immobilized water (shifted to 166 ms). These findings confirm that manipulating COS chain length regulates aggregate subpopulations, offering a targeted strategy for fabricating mechanically robust plant protein gels.